The advent of Polymerase Chain Reaction (PCR) since 1983 has revolutionized molecular biology through vastly extending the capability to identify, manipulate, and reproduce DNA. Nowadays PCR is routinely practiced in the course of conducting scientific researches, clinical diagnostics, forensic identifications, and environmental studies. PCR has been automated through the use of thermal stable DNA polymerases and a machine commonly known as “thermal cycler”.
Performing a large quantity of PCR with the conventional thermal cycler has been rather expensive. This is partly due to the intrinsic limitations of the conventional instrument. The conventional thermal cycler employs metal heating blocks and cooling reservoirs to carry out the thermal cycling of reaction samples in plastic microfuge tubes. Because the instrument has a large thermal mass and the plastic tubes have low heat conductivity, high level of electrical power is required to operate the instrument.
In recent years, the advancement in microfabrication technology enabled the production of miniaturized devices integrated with electrical, optical, chemical or mechanical elements. The technology embodies a range of fabrication techniques including low-pressure vapor deposition, photolithography, and etching. Based on these techniques, miniaturized devices containing silicon channels coupled to micro-heaters have been proposed (see, e.g., U.S. Pat. Nos. 5,639,423, 5,589,136 and 5,587,128). While the channel- or chamber-based design in principle reduces the thermal mass and the reaction volume, it still suffers from other practical drawbacks. In particular, the channels or chambers by design are not amenable to automated sealing that prevents evaporation and/or cross contamination of the reaction samples.
There thus remains a considerable need for small, mass produced, and disposable devices designed to perform high-throughput amplification of nucleic acids. A desirable device would allow (a) multiplexing an enormous quantity of amplification reactions; (b) automated and targeted sealing of the reaction sites on the devices; and (c) monitoring the progress of the amplification reaction in real time. The present invention satisfies these needs and provides related advantages as well.